Based upon in vivo data, this study will demonstrate the nuclear and cytoplasmic sites of estrogen and progesterone receptors in the mouse oviduct. It will compare the effects upon the number and locations of the receptor sites of cyclic endogenous estrogen and progesterone of mature mice and of exogenous ovarian hormones given to immature mice. The study is designed to provide basic data on sites of hormonal activities in the oviduct.